The present invention relates to certain 2-amino-6-(2,4,5-substituted-phenyl)-pyridines, to pharmaceutical compositions containing them and to their use in the treatment and prevention of central nervous system and other disorders The compounds of this invention exhibit activity as nitric oxide synthase (NOS) inhibitors.
There are three known isoforms of NOSxe2x80x94an inducible form (I-NOS) and two constitutive forms referred to as, respectively, neuronal NOS (N-NOS) and endothelial NOS (E-NOS). Each of these enzymes carries out the conversion of arginine to citrulline while producing a molecule of nitric oxide (NO) in response to various stimuli. It is believed that excess nitric oxide (NO) production by NOS plays a role in the pathology of a number of disorders and conditions in mammals. For example, NO produced by I-NOS is thought to play a role in diseases that involve systemic hypotension such as toxic shock and therapy with certain cytokines. It has been shown that cancer patients treated with cytokines such as interleukin 1 (IL-1), interleukin 2 (IL-2) or tumor necrosis factor (TNF) suffer cytokine-induced shock and hypotension due to NO produced from macrophages, i.e., inducible NOS (I-NOS), see Chemical and Engineering News, December 20, p. 33, (1993). I-NOS inhibitors can reverse this. It is also believed that I-NOS plays a role in the pathology of diseases of the central nervous system such as ischemia. For example, inhibition of I-NOS has been shown to ameliorate cerebral ischemic damage in rats, see Am. J. Physiol., 268, p. R286 (1995)). Suppression of adjuvant induced arthritis by selective inhibition of I-NOS is reported in Eur. J. Pharmacol., 273, p. 15-24 (1995).
NO produced by N-NOS is thought to play a role in diseases such as cerebral ischemia, pain, and opiate tolerance. For example, inhibition of N-NOS decreases infarct volume after proximal middle cerebral artery occlusion in the rat, see J. Cerebr. Blood Flow Metab., 14, p. 924-929 (1994). N-NOS inhibition has also been shown to be effective in antinociception, as evidenced by activity in the late phase of the formalin-induced hindpaw licking and acetic acid-induced abdominal constriction assays, see Br. J. Pharmacol., 110, p. 219-224 (1993). Finally, opioid withdrawal in rodents has been reported to be reduced by N-NOS inhibition, see Neuropsychopharmacol., 13, p. 269-293 (1995).
Other NOS inhibitors and their utility as pharmaceutical agents in the treatment of central nervous system disorders and other disorders are referred to in the following references: U.S. patent application Ser. No. 09/325,480, filed Jun. 3, 1999, allowed Nov. 14, 2000, U.S. patent application Ser. No. 09/802,086, filed Mar. 8, 2001, and counterpart International Patent Application No. WO 98/24766, published Jun. 11, 1998; U.S. Pat. No. 6,235,747, issued May 22, 2001, U.S. patent application Ser. No. 09/826,132, filed Apr. 4, 2001, and counterpart International Patent Application No. WO 97/36871, published Oct. 9, 1997; U.S. patent application Ser. No. 09/740,385, filed Dec. 20, 2000, and counterpart International Patent Application No. WO 99/10339, published Mar. 4, 1999; U.S. patent application Ser. No. 09/381,887, filed Mar. 28, 2000, and counterpart International Patent Application No. WO 99/11620, published Mar. 11, 1999; U.S. patent application Ser. No. 09/127,158, filed Jul. 31, 1998, and counterpart International Patent Application No. WO 98/34919, published Aug. 13, 1998; and U.S. patent application Ser. No. 09/403,177, filed Oct. 18, 1999, and counterpart International Patent Application No. WO 99/62883, published Dec. 9, 1999.
The present invention relates to a compound, or pharmaceutically acceptable salt thereof, that is selected from the following compounds and their pharmaceutically acceptable salts:
(a) 6-[4-(N-methyl-3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, which has the following structure 
(b) 6-[4-(N,N-dimethylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, which has the following structure 
(c) 6-[4-(N-methylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, which has the following structure 
(d) 6-[4-(3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, which has the following structure 
In so far as the compounds of formulas I, II, III and IV of this invention contain basic groups, they can form acid addition salts with various inorganic and organic acids. The present invention also relates to the pharmaceutically acceptable acid addition salts of compounds of the formulas I, II, III and IV. Although such salts must be pharmaceutically acceptable for administration to animals, it is often desirable in practice to initially isolate the base compound from the reaction mixture as a pharmaceutically unacceptable salt and then simply convert to the free base compound by treatment with an alkaline reagent, and thereafter, convert the free base to a pharmaceutically acceptable acid addition salt. The acid addition salts of the base compounds of this invention are readily prepared by treating the base compound with a substantially equivalent amount of the chosen mineral or organic acid in an aqueous solvent or in a suitable organic solvent, such as methanol or ethanol. Upon careful evaporation of the solvent, the desired solid salt is readily obtained. The acids which are used to prepare the pharmaceutically acceptable acid addition salts of the aforementioned base compounds of this invention are those which form non-toxic acid addition salts, i.e., salts containing pharmaceutically acceptable anions, such as the hydrochloride, hydrobromide, hydroiodide, nitrate, sulfate or bisulfate, phosphate or acid phosphate, acetate, lactate, citrate or acid citrate, tartrate or bi-tartrate, succinate, maleate, fumarate, gluconate, saccharate, benzoate, methanesulfonate, ethanesulfonate, benzenesulfonate, p-toluenesulfonate and pamoate (i.e., 1,1xe2x80x2-methylene-bis-(2-hydroxy-3-naphthoate))salts.
The present invention also includes isotopically-labeled compounds that are identical to those recited in formulas I, II, III and IV, but for the fact that one or more atoms are replaced by an atom having an atomic mass or mass number different from the atomic mass or mass number usually found in nature. Examples of isotopes that can be incorporated into the compounds of the present invention include isotopes of hydrogen, carbon, nitrogen and oxygen, such as 2H, 3H, 13C, 11C, 14C, 15N, 18O, 17O, respectively. The compounds of the present invention, prodrugs thereof, and pharmaceutically acceptable salts of such compounds or of such prodrugs which contain the aforementioned isotopes and/or other isotopes are within the scope of this invention. Such compounds may be useful as research and diagnostic tools in metabolism pharmacokinetic studies and in binding assays. Certain isotopically-labeled compounds of the present invention, for example, those into which radioactive isotopes such as 3H and 14C are incorporated, are useful in drug and/or substrate tissue distribution assays. Tritiated, i.e., 3H, and carbon-14, i.e., 14C, isotopes are particularly preferred for their ease of preparation and detectability. Further, substitution with heavier isotopes such as deuterium, i.e., 2H, can afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements and, hence, may be preferred in some circumstances. Isotopically-labeled compounds of the present invention and prodrugs thereof can generally be prepared by carrying out the procedures disclosed in the schemes and discussion of the schemes and/or in the examples and preparations described herein, by substituting a readily available isotopically-labeled reagent for a nonisotopically-labeled reagent.
More specific embodiments of this invention relate to a compound of the formula I, which has the chemical name 6-[4-(N-methyl-3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, and the pharmaceutically acceptable salts of such compound.
Other more specific embodiments of this invention relate to a compound of the formula II, which has the chemical name 6-[4-(N,N-dimethylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, and the pharmaceutically acceptable salts of such compound.
Other more specific embodiments of this invention relate to a compound of the formula III, which has the chemical name 6-[4-(N-methylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, and the pharmaceutically acceptable salts of such compound.
Other more specific embodiments of this invention relate to a compound of the formula IV, which has the chemical name 6-[4-(3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, and the pharmaceutically acceptable salts of such compound.
The compounds of formulas I, II, III and IV of this invention, and their pharmaceutically acceptable salts, have useful pharmaceutical and medicinal properties. The compounds of formulas I, II, III and IV, and their pharmaceutically acceptable salts, are useful as NOS inhibitors i.e., they possess the ability to inhibit the NOS enzyme in mammals, and therefore they are able to function as therapeutic agents in the treatment of the disorders and diseases enumerated below in an afflicted mammal.
The term xe2x80x9ctreating,xe2x80x9d as used herein, refers to reversing, alleviating, or inhibiting the progress of the disease, disorder or condition, or one or more symptoms of such disease, disorder or condition, to which such term applies. Depending on the condition of the patient, as used herein, this term also refers to preventing a disease, disorder or condition, and includes preventing the onset of a disease, disorder or condition, or preventing the symptoms associated with a disease, disorder or condition. As used herein, this term also refers to reducing the severity of a disease, disorder or condition or symptoms associated with such disease, disorder or condition prior to affliction with the disease, disorder or condition. Such prevention or reduction of the severity of a disease, disorder or condition prior to affliction refers to administration of the composition of the present invention, as described herein, to a subject that is not at the time of administration afflicted with the disease, disorder or condition. xe2x80x9cPreventingxe2x80x9d also refers to preventing the recurrence of a disease, disorder or condition or of one or more symptoms associated with such disease, disorder or condition. The terms xe2x80x9ctreatmentxe2x80x9d and xe2x80x9ctherapeutically,xe2x80x9d as used herein, refer to the act of treating, as xe2x80x9ctreatingxe2x80x9d is defined above.
The present invention also relates to a pharmaceutical composition for treating a condition selected from the group consisting of migraine, inflammatory diseases (e.g., asthma, psoriasis, eczema, arthritis), stroke, acute, chronic and neuropathic pain, hypovolemic shock, traumatic shock, reperfusion injury, Crohn""s disease, ulcerative colitis, septic shock, multiple sclerosis, AIDS associated dementia, neurodegenerative diseases, neuron toxicity, Alzheimer""s disease, chemical dependencies and addiction (e.g., dependencies on drugs, alcohol and nicotine), emesis, epilepsy, anxiety, psychosis, head trauma, adult respiratory distress syndrome (ARDS), morphine induced tolerance and withdrawal symptoms, inflammatory bowel disease, osteoarthritis, rheumatoid arthritis, ovulation, dilated cardiomyopathy, acute spinal cord injury, Huntington""s disease, Parkinson""s disease, glaucoma, macular degeneration, diabetic neuropathy, diabetic nephropathy and cancer in a mammal, including a human, comprising an amount of a compound of the formula I, II, III or IV, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising an amount of a compound of the formula I, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising an amount of a compound of the formula II, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising an amount of a compound of the formula III, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising an amount of a compound of the formula IV, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition, and a pharmaceutically acceptable carrier.
The present invention also relates to a method of treating a condition selected from the group consisting of migraine, inflammatory diseases (e.g., asthma, psoriasis, eczema, arthritis), stroke, acute, chronic and neuropathic pain, hypovolemic shock, traumatic shock, reperfusion injury, Crohn""s disease, ulcerative colitis, septic shock, multiple sclerosis, AIDS associated dementia, neurodegenerative diseases, neuron toxicity, Alzheimer""s disease, chemical dependencies and addictions (e.g., dependencies on drugs, alcohol and nicotine), emesis, epilepsy, anxiety, psychosis, head trauma, adult respiratory distress syndrome (ARDS), morphine induced tolerance and withdrawal symptoms, inflammatory bowel disease, osteoarthritis, rheumatoid arthritis, ovulation, dilated cardiomyopathy, acute spinal cord injury, Huntington""s disease, Parkinson""s disease, glaucoma, macular degeneration, diabetic neuropathy, diabetic nephropathy and cancer in a mammal, including a human, comprising administering to said mammal an amount of a compound of the formula I, II, III or IV, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal an amount of a compound of the formula I, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal an amount of a compound of the formula II, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal an amount of a compound of the formula III, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal an amount of a compound of the formula IV, or a pharmaceutically acceptable salt thereof, that is effective in treating such condition.
The present invention also relates to a pharmaceutical composition for inhibiting nitric oxide synthase (NOS) in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula I, II, III or IV, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for inhibiting NOS in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula I, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for inhibiting NOS in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula II, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for inhibiting NOS in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula III, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for inhibiting NOS in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula IV, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
The present invention also relates to a method of inhibiting NOS in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of inhibiting NOS in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula I, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of inhibiting NOS in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula II, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of inhibiting NOS in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula III, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of inhibiting NOS in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula IV, or a pharmaceutically acceptable salt thereof.
The present invention also relates to a pharmaceutical composition for treating a condition selected from the group consisting of migraine, inflammatory diseases (e.g., asthma, psoriasis, arthritis, eczema), stroke, acute, chronic and neuropathic pain, hypovolemic shock, traumatic shock, reperfusion injury, Crohn""s disease, ulcerative colitis, septic shock, multiple sclerosis, AIDS associated dementia, neurodegenerative diseases, neuron toxicity, Alzheimer""s disease, chemical dependencies and addictions (e.g., dependencies on drugs, alcohol and nicotine), emesis, epilepsy, anxiety, psychosis, head trauma, adult respiratory distress syndrome (ARDS), morphine induced tolerance and withdrawal symptoms, inflammatory bowel disease, osteoarthritis, rheumatoid arthritis, ovulation, dilated cardiomyopathy, acute spinal cord injury, Huntington""s disease, glaucoma, macular degeneration, diabetic neuropathy, diabetic nephropathy and cancer in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula I, II, III or IV, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula I, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula II, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula III, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
This invention also relates to the above pharmaceutical composition for treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising a NOS inhibiting effective amount of a compound of the formula IV, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
The present invention also relates to a method of treating a condition selected from the group consisting of migraine, inflammatory diseases (e.g., asthma, psoriasis, eczema, arthritis), stroke, acute, chronic and neuropathic pain, hypovolemic shock, traumatic shock, reperfusion injury, Crohn""s disease, ulcerative colitis, septic shock, multiple sclerosis, AIDS associated dementia, neurodegenerative diseases, neuron toxicity, Alzheimer""s disease, chemical dependencies and addictions (e.g., dependencies on drugs, alcohol or nicotine), emesis, epilepsy, anxiety, psychosis, head trauma, adult respiratory distress syndrome (ARDS), morphine induced tolerance and withdrawal symptoms, inflammatory bowel disease, osteoarthritis, rheumatoid arthritis, ovulation, dilated cardiomyopathy, acute spinal cord injury, Huntington""s disease, Parkinson""s disease, glaucoma, macular degeneration, diabetic neuropathy, diabetic nephropathy and cancer in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula I, II, III or IV, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula I, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula II, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula III, or a pharmaceutically acceptable salt thereof.
This invention also relates to the above method of treating a condition selected from the group of conditions referred to above, in a mammal, including a human, comprising administering to said mammal a NOS inhibiting effective amount of a compound of the formula IV, or a pharmaceutically acceptable salt thereof.
In the reaction schemes and discussion that follow, formulas I, II, III and IV are defined as set forth above in the Summary of the Invention.
Compounds of the formulas I and IV, and their pharmaceutically acceptable salts, may be prepared as described in the following reaction schemes and discussion, and as described in U.S. patent application Ser. No. 09/127,158, filed Jul. 31, 1998, entitled 2-Amino-6-(2-substituted-4-phenoxy)-substituted-pyridines, and counterpart International Patent Application No. WO 98/34919, published Aug. 13, 1998. The foregoing patent applications are incorporated herein by reference in their entirety. 
Scheme 1 illustrates a method for preparing the compound 6-[4-(N-methyl-3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, the compound of the formula I, and 6-[4-(3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, the compound of the formula II. These compounds are referred to in Scheme 1 as compounds of the formula xe2x80x9c(I)xe2x80x9d (or xe2x80x9c(12)xe2x80x9d) and xe2x80x9c(IV)xe2x80x9d (or (xe2x80x9c(11)xe2x80x9d), respectively.
The following reactions, which are illustrated in Scheme 1, are preferably conducted under a nitrogen atmosphere (unless otherwise indicated).
Referring to Scheme 1, 2-acetyl-5-methoxyphenol (1) may be reduced to 2-ethyl-5-methoxyphenol (2) by the methods described in Chem. Pharm. Bull. (Japan), 27 (1979) 1490-94. For example, 2-acetyl-5-methoxyphenol (1) can be treated with a reducing agent such as sodium borohydride in tetrahydrofuran (THF) along with a base such as triethylamine and an acylating agent such as ethyl chloroformate. Other tertiary amines and chloroformates can be used. While THF is the preferred solvent, diethyl ether can also be used. This reaction can be carried out at a temperature from about 0xc2x0 C. to about 10xc2x0 C., preferably about 0xc2x0 C.
The alcohol group in the 2-ethyl-5-methoxyphenol (2) is protected by conversion to 3-benzyloxy-4-ethyl-1-methoxybenzene (3). More specifically 2-ethyl-5-methoxyphenol (2) is allowed to react with benzyl bromide and potassium carbonate in a polar solvent such as acetonitrile, dimethylformamide (DMF) or acetone, preferably acetone. The reaction yields 3-benzyloxy-4-ethyl-1-methoxybenzene (3). This reaction can be carried out at a temperature from about room temperature to about 60xc2x0 C., preferably about 60xc2x0 C.
Alternatively, 2-ethyl-5-methoxyphenol (2) may be allowed to react with benzyl bromide and potassium hydroxide in a polar solvent such as acetonitrile, dimethylsulfoxide (DMSO) or dimethylformamide (DMF), preferably acetonitrile. In this alternative reaction, a catalyst such as dibenzo-18-crown-6 may be used. This reaction also yields 3-benzyloxy-4-ethyl-1-methoxybenzene (3). The reaction is generally carried out at a temperature from about room temperature to about the reflux temperature of the reaction mixture, preferably at about the reflux temperature of the reaction mixture.
In a bromination reaction, the 3-benzyloxy-4-ethyl-1-methoxybenzene (3) is combined with N-bromosuccinimide (NBS) and silica gel 60 (EM Science, 480 Democrat Road, Gibbstown, N.J. 08027, an affiliate of Merck KGaA, Darmstadt, Germany) in a nonpolar solvent such as carbon tetrachloride at a temperature from about 0xc2x0 C. to about room temperature. Preferably, the reaction is conducted at about room temperature. This reaction is allowed to stir, in the absence of light, to yield 5-benzyloxy-2-bromo-4-ethyl-1-methoxybenzene (4).
The resulting 5-benzyloxy-2-bromo-4-ethyl-1-methoxybenzene (4) is allowed to react with n-butyl lithium in a polar solvent such as ether, glyme or tetrahydrofuran (THF), preferably THF, at a temperature of about xe2x88x9278xc2x0 C. Triethyl borate is then added to the reaction mixture, and the reaction mixture is allowed to stir at a temperature of about xe2x88x9278xc2x0 C. The reaction mixture is then allowed to warm to about room temperature. The reaction yields 4-benzyloxy-5-ethyl-2-methoxy-phenylboronic acid (5).
Reacting the 4-benzyloxy-5-ethyl-2-methoxy-phenylboronic acid (5) with 2-bromo-6-(2,5-dimethylpyrrol-1-yl)pyridine, sodium carbonate and tetrakis(triphenylphosphine)palladium(0) in a polar solvent such as methanol/water, ethanol/water, or tetrahydrofuran (THF)/water, preferably ethanol/water, at a temperature from about room temperature to about the reflux temperature of the reaction mixture, preferably at about the reflux temperature, yields 2-(4-benzyloxy-5-ethyl-2-methoxy-phenyl)-6-(2,5-dimethyl-pyrrol-1-yl)-pyridine (6).
Alternatively, the 2-bromo-6-(2,5-dimethylpyrrol-1-yl)pyridine in the above reaction may be replaced with a compound having the structural formula 
wherein P is a nitrogen protecting group such as trimethylacetyl or another appropriate nitrogen protecting group. Such protecting groups are well known to those of skill in the art. For example, nitrogen protecting groups are discussed in Greene, Theodora W. and Wuts, Peter G. M., Protective Groups In Organic Synthesis, Second Edition, John Wiley and Sons, Inc., New York, 1991 at pages 309-405. The above compounds are either commercially available, known in the scientific literature or easily obtained using well known methods and reagents.
The benzyl protecting group can be removed from the 2-(4-benzyloxy-5-ethyl-2-methoxy-phenyl)-6-(2,5-dimethyl-pyrrol-1-yl)-pyridine (6) by reacting this compound with ammonium formate in a polar solvent such as water or a lower alcohol solvent (e.g., methanol or ethanol), or in a mixture of one or more of these solvents, preferably methanol, at a temperature from about room temperature to about the reflux temperature of the reaction mixture. This reaction is preferably carried out at about the reflux temperature in the presence of about 20% palladium hydroxide on carbon. The aminopyridine protecting group is then removed from the resulting 4-[6-(2,5-dimethyl-pyrrol-1-yl)-pyridin-2-yl]-6-ethyl-3-methoxyphenol (7) in a conversion to 4-(6-amino-pyridin-2-yl)-2-ethyl-5-methoxyphenol (8). The 4-[6-(2,5-dimethyl-pyrrol-1-yl)-pyridin-2-yl]-6-ethyl-3-methoxyphenol (7) is converted to 4-(6-amino-pyridin-2-yl)-2-ethyl-5-methoxyphenol (8) by reacting it with hydroxylamine in a polar solvent such as water, a lower alcohol, such as methanol or ethanol, or a mixture of these solvents, preferably methanol/water. This reaction is conducted at a temperature from about room temperature to about the reflux temperature of the solvent, preferably at about the reflux temperature.
The 4-(6-amino-pyridin-2-yl)-2-ethyl-5-methoxyphenol (8) is treated with potassium t-butoxide and allowed to react with 3-methanesulfonyloxy-azetidine-1-carboxylic acid tert-butyl ester in a polar solvent such as dimethylsulfoxide (DMSO), dimethylformamide (DMF) or 1-methyl-2-pyrrolidinone, preferably DMSO, to form 6-[4-(3-azetidinoxy-1-carboxylic acid tert-butyl ester)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (10). Other nitrogen protecting groups such as xe2x80x94C(xe2x95x90O)OCH2C6H5, trifluoroacetyl and COOR (wherein R is benzyl, phenyl, alkyl, formyl or a similar group) can be used to protect the azetidine nitrogen. In addition, the mesylate leaving group can be replaced with another appropriate leaving group such as tosylate, trifluoroacetate or triflate. Other bases such as lithium t-butoxide can also be used. Preferably, a catalytic amount of tetrabutylammonium iodide (TBAI) is added to the reaction mixture. Other catalysts such as tetrabenzylammonium iodide and benzyltrimethylammonium iodide may also be used. This alkylation reaction is typically carried out in the presence of an alkali metal alkoxide such as lithium or potassium tert-butoxide, preferably potassium tert-butoxide, in a high boiling polar organic solvent such as DMSO, DMF or 1-methyl-2-pyrrolidinone, preferably DMSO. The reaction temperature can range from about 50xc2x0 C. to about 100xc2x0 C., and is preferably about 100xc2x0 C.
Alternatively, 4-(6-amino-pyridin-2-yl)-2-ethyl-5-methoxyphenol (8) may be reacted with a compound having the structural formula 
using triphenylphosphine and diethylazodicarboxylate or a water soluble azodicarboxylate in tetrahydrofuran (THF) under standard Mitsunobo reaction conditions to yield 6-[4-(3-azetidinoxy-1-carboxylic acid tert-butyl ester)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (10). Typically, the reactants are combined at about 0xc2x0 C. and then allowed to warm to room temperature.
Reduction of the 6-[4-(3-azetidinoxy-1-carboxylic acid tert-butyl ester)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (10) yields the compound of formula I, 6-[4-(N-methyl-3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (12). This reduction is preferably accomplished using lithium aluminum hydride as the reducing agent and tetrahydrofuran (THF) or another organic ether (e.g., ethyl ether or glyme) as the solvent. Other aluminum hydride reducing agents can also be used, such as diisobutyl aluminum hydride. Diborane can also be used as the reducing agent. The foregoing reaction is generally conducted at a temperature from about room temperature to about the reflux temperature of the reaction mixture, preferably at about the reflux temperature.
Alternatively, the 6-[4-(3-azetidinoxy-1-carboxylic acid tert-butyl ester)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (10) may be deprotected to yield the compound of formula IV, (6-[4-(3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (11). This transformation is preferably accomplished using trifluoroacetic acid (TFA) as the acid catalyst, either neat or in a polar solvent such as dichloromethane, chloroform or dichloroethane, preferably dichloromethane. Other acid catalysts can also be used, such as hydrochloric acid, hydrobromic acid or toluenesulfonic acid. This reaction is generally conducted at a temperature from about 0xc2x0 C. to about room temperature, preferably at about room temperature.
The compound of formula IV, 6-[4-(3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (11), may itself be converted to the compound of formula I, 6-[4-(N-methyl-3-azetidinoxy)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (12), by reductive amination. This reductive amination is preferably accomplished using formaldehyde, acetic acid and sodium triacetoxy borohydride as the reducing agent and acetonitrile/water, dichloromethane or methanol, preferably acetonitrile/water, as the solvent. Other reducing agents can also be used, such as sodium cyanoborohydride. The above reaction is generally conducted at a temperature from about 0xc2x0 C. to about room temperature, preferably at about room temperature.
The starting materials used in the procedures of Scheme 1, the syntheses of which are not described above, are either commercially available, known in the art or readily obtainable from known compounds using methods that will be apparent to those skilled in the art.
The compounds of formulas I and IV, and the intermediates shown in the above reaction schemes, can be isolated and purified by conventional procedures, such as recrystallization or chromatographic separation.
Compounds of the formulas II and III, and their pharmaceutically acceptable salts, may be prepared as described in the following reaction schemes and discussion. 
Scheme 2 illustrates a method for preparing the compound 6-[4-(N,N-dimethylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, the compound of the formula II, and 6-[4-(N-methylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine, the compound of the formula III. These compounds are referred to in Scheme 2 as compounds of the formulas xe2x80x9c(II)xe2x80x9d (or xe2x80x9c(23)xe2x80x9d) and xe2x80x9c(III)xe2x80x9d (or xe2x80x9c(25)xe2x80x9d), respectively.
The following reactions, which are illustrated in Scheme 2, are preferably conducted under a nitrogen atmosphere (unless otherwise indicated).
Referring to Scheme 2, 2-bromo-5-methoxybenzoic acid is reduced to 2-bromo-5-methoxybenzyl alcohol (13) using borane (1 M in tetrahydrofuran (THF)) in a solvent such as THF, diethyl ether or diglyme, preferably THF. Other suitable reducing agents that may be used in the above transformation include BH3.SMe2 and lithium aluminum hydride/aluminum chloride. The reduction may be carried out at a temperature from about 0xc2x0 C. to about room temperature, preferably about 0xc2x0 C.
The alcohol group in the 2-bromo-5-methoxybenzyl alcohol (13) is protected by conversion to 2-bromo-5-methoxy-benzyloxy)-tert-butyl-dimethyl-silane (14). More specifically, 2-bromo-5-methoxybenzyl alcohol (13) is converted to 2-bromo-5-methoxy-benzyloxy)-tert-butyl-dimethyl-silane (14) with imidazole and t-butyl dimethylsilylchloride(TBDMSCI), or TBDMSOSO2CF3, in a solvent such as tetrahydrofuran (THF), dimethylformamide (DMF) or methylene chloride, preferably anhydrous THF, at a temperature from about 0xc2x0 C. to about room temperature, preferably about room temperature.
In a Stille coupling reaction, 2-bromo-5-methoxy-benzyloxy)-tert-butyl-dimethyl-silane (14) is converted to tert-butyl-dimethyl-(2-vinyl-5-methoxy-benzyloxy)-silane (15). The conversion is carried out using tributylvinyl tin in a solvent such as toluene, dimethylformamide (DMF), acetone, xylene or benzene, preferably toluene, at a temperature from about room temperature to about 100xc2x0 C., preferably about 100xc2x0 C. A palladium catalyst such as tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4), BnPdCl(PPh3)2, or PdCl2(PPh3)2, preferably Pd(PPh3)4, may be used.
Tert-butyl-dimethyl-(2-vinyl-5-methoxy-benzyloxy)-silane (15) is reduced to tert-butyl-dimethyl-(2-ethyl-5-methoxy-benzyloxy)-silane (16) using a hydrogenation catalyst, preferably platinum oxide, under a hydrogen pressure of about 1 to 4 atmospheres, preferably under a hydrogen pressure of about 2 atmospheres. Suitable solvents include methanol, ethanol, ethyl acetate and acetic acid, preferably ethyl acetate. Catalysts such as 10% palladium (Pd) on calcium carbonate, Rhxe2x80x94C or Pdxe2x80x94C may also be used. The reaction is generally carried out at about room temperature.
In a bromination reaction, tert-butyl-dimethyl-(2-ethyl-5-methoxy-benzyloxy)-silane (16) is converted to tert-butyl-dimethyl-(4-bromo-2-ethyl-5-methoxy-benzyloxy)-silane (17) using N-bromosuccinimide (NBS) followed by the addition of silica gel 60 (EM Science, 480 Democrat Road, Gibbstown, N.J. 08027, an affiliate of Merck KGaA, Darmstadt, Germany). The reaction is allowed to stir in the absence of light. The reaction may also be carried out using NBS without silica gel, or using bromine instead of NBS. Suitable solvents include carbon tetrachloride, chloroform, acetic acid and carbon disulfide, preferably carbon tetrachloride. The reaction may be carried out at about room temperature.
Tert-butyl-dimethyl-(4-bromo-2-ethyl-5-methoxy-benzyloxy)-silane (17) is cooled to about xe2x88x9278xc2x0 C. in tetrahydrofuran (THF) and treated with n-butyl lithium. The reaction mixture is then treated with triethyl borate, at about xe2x88x9278xc2x0 C., and allowed to warm to room temperature. Following acid workup, the reaction mixture yields tert-butyl-dimethyl-(4-boronic acid-2-ethyl-5-methoxy-benzyloxy)-silane (18). THF is the preferred solvent, but other suitable solvents such as diethyl ether may also be used. Similarly, n-butyl lithium is the preferred reagent, but other suitable reagents such as t-butyl lithium may also be used.
In a Suzuki coupling reaction, 2-bromo-6-(N-2,2-dimethylpropamido)pyridine and tert-butyl-dimethyl-(4-boronic acid-2-ethyl-5-methoxy-benzyloxy)-silane (18) are treated with sodium carbonate and tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) in ethanol and water. The reaction is heated to reflux to yield 2-2-(4-tert-butyldimethylsilyloxymethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (19). Tetrakis(triphenylphosphine)palladium(0) is the preferred catalyst. However, other suitable palladium catalysts include Pd(OAc)2, Pd2(dba)3 and [(allyl)PdCl]2. Similarly, ethanol/water is the preferred solvent, but other suitable solvents such as tetrahydrofuran (THF), acetone, benzene and dimethoxyethane (DME) may be used.
The tert-butyl-dimethylsilyl protecting group is removed from the 2-2-(4-tert-butyldimethylsilyloxymethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (19) by treatment with 1M tetrabutylammonium fluoride (TBAF) in tetrahydrofuran (THF) at about room temperature. The reaction yields 2-(4-hydroxymethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (20). Although TBAF is the preferred reagent, other reagents such as KF/18-crown-6 and TBACl/KF may also be used. Similarly, although THF is the preferred solvent, other solvents such as diethyl ether and acetonitrile may be used.
The alcohol, 2-(4-hydroxymethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (20), is oxidized to the corresponding aldehyde, 2-(4-formyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (21), by treatment with manganese dioxide in toluene. In addition to the preferred catalyst, manganese dioxide, other suitable catalysts include BaMnO4 and AgMnO4. Benzene may also be used as the solvent in the above reaction, although toluene is preferred. The above reaction is carried out at a temperature from about room temperature to about 100xc2x0 C., preferably about 90xc2x0 C.
Reductive amination of the aldehyde, 2-(4-formyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (21), with N,N-dimethylamine yields the amine, 2-(4-N,N-dimethylaminomethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (22). This reductive amination is accomplished by treating 2-(4-formyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (21) in dichloromethane with N,N-dimethylamine in tetrahydrofuran (THF), sodium triacetoxyborohydride and acetic acid at about room temperature. Other suitable reducing agents include sodium cyanoborohydride.
The aminopyridine protecting group is removed from the 2-(4-N,N-dimethylaminomethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (22) by treatment with 6N hydrogen chloride in dioxane at a temperature from about room temperature to about the reflux temperature, preferably at about the reflux temperature. The reaction yields the compound of formula II, 6-[4-(N,N-dimethylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (23). Aside from the 6N hydrogen chloride, which is preferred, other reagents that may be used in the above reaction include sodium hydroxide/methanol and barium hydroxide/methanol. Aside from dioxane, which is also preferred, other solvents that may be used include methanol/water and ethanol/water.
Alternatively, reductive amination of the aldehyde, 2-(4-formyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (21), with N-methylamine yields the amine, 2-(4-N-methylaminomethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (24). This reductive amination is accomplished by combining 2-(4-formyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (21) in dichloromethane with N-methylamine in tetrahydrofuran (THF), acetic acid and sodium triacetoxyborohydride. The reaction is carried out at a temperature from about 0xc2x0 C. to about room temperature, preferably about room temperature. Other suitable reducing agents include sodium cyanoborohydride.
The aminopyridine protecting group is removed from the 2-(4-N-methylaminomethyl-5-ethyl-2-methoxy-phenyl)-6-(N-2,2-dimethylpropamido)-pyridine (24) by treatment with dioxane and 6N hydrogen chloride at a temperature of about room temperature to about the reflux temperature, preferably at about the reflux temperature. The reaction yields the compound of formula III, 6-[4-(N-methylaminomethyl)-5-ethyl-2-methoxy-phenyl]-pyridin-2-ylamine (25). Aside from the 6N hydrogen chloride, which is preferred, other reagents which may be used in the above reaction include sodium hydroxide/methanol and barium hydroxide/methanol. Aside from dioxane, which is also preferred, other solvents which may be used include methanol/water and ethanol/water.
The starting materials used in the procedures of Scheme 2, the syntheses of which are not described above, are either commercially available, known in the art or readily obtainable from known compounds using methods that will be apparent to those skilled in the art.
The compounds of formulas II and III, and the intermediates shown in the above reaction schemes can be isolated and purified by conventional procedures, such as recrystallization or chromatographic separation.
In each of the reactions discussed or illustrated above, pressure is not critical unless otherwise indicated. Pressures from about 0.5 atmospheres to about 5 atmospheres are generally acceptable, and ambient pressure, i.e., about 1 atmosphere, is preferred as a matter of convenience.
This invention relates to the compounds of formulas I, II, III and IV, and their pharmaceutically acceptable salts. The compounds of formulas I, II, III, and IV, and their pharmaceutically acceptable salts, are hereinafter collectively referred to as xe2x80x9cthe active compounds of the present invention.xe2x80x9d The active compounds of the present invention can be administered to mammals via either the oral, parenteral (such as subcutaneous, intravenous, intramuscular, intrasternal and infusion techniques), rectal, intranasal or topical routes. In general, these compounds are most desirably administered in doses ranging from about 0.01 mg to about 1500 mg per day, in single or divided doses (i.e., from 1 to 4 doses per day), although variations will necessarily occur depending upon the species, weight and condition of the subject being treated and the particular route of administration chosen. However, a dosage level that is in the range of about 0.5 mg to about 500 mg per kg of body weight per day is most desirably employed. Nevertheless, variations may occur depending upon the species of animal being treated and its individual response to said medicament, as well as on the type of pharmaceutical formulation chosen and the time period and interval at which such administration is carried out. In some instances, dosage levels below the lower limit of the aforesaid range may be more than adequate, while in other cases still larger doses may be employed without causing any harmful side effects, provided that such higher dosage levels are first divided into several small doses for administration throughout the day.
The active compounds of the present invention may be administered alone or in combination with pharmaceutically acceptable carriers or diluents by either of the routes previously indicated, and such administration may be carried out in single or multiple doses. More particularly, the active compounds of the present invention can be administered in a wide variety of different dosage forms, i.e., they may be combined with various pharmaceutically acceptable inert carriers in the form of tablets, capsules, lozenges, troches, hard candies, powders, sprays, creams, salves, suppositories, jellies, gels, pastes, lotions, ointments, aqueous suspensions, injectable solutions, elixirs, syrups, and the like. Such carriers include solid diluents or fillers, sterile aqueous media and various non-toxic organic solvents, etc. Moreover, oral pharmaceutical compositions can be suitably sweetened and/or flavored. In general, the therapeutically effective compounds of this invention are present in such dosage forms at concentration levels ranging from about 5.0% to about 70% by weight.
For oral administration, tablets containing various excipients such as microcrystalline cellulose, sodium citrate, calcium carbonate, dicalcium phosphate and glycine may be employed along with various disintegrants such as starch (preferably corn, potato or tapioca starch), alginic acid and certain complex silicates, together with granulation binders such as polyvinylpyrrolidone, sucrose, gelatin and acacia. Additionally, lubricating agents such as magnesium stearate, sodium lauryl sulfate and talc are often very useful for tabletting purposes. Solid compositions of a similar type may also be employed as fillers in gelatin capsules. Preferred materials in this connection include lactose or milk sugar as well as high molecular weight polyethylene glycols. When aqueous suspensions and/or elixirs are desired for oral administration, the active ingredient may be combined with various sweetening or flavoring agents, coloring matter or dyes, and, if so desired, emulsifying and/or suspending agents as well, together with such diluents as water, ethanol, propylene glycol, glycerin and various like combinations thereof.
For parenteral administration, solutions containing an active compound of the present invention in either sesame or peanut oil or in aqueous propylene glycol may be employed. The aqueous solutions should be suitably buffered (preferably pH greater than 8) if necessary and the liquid diluent first rendered isotonic. These aqueous solutions are suitable for intravenous injection purposes. The oily solutions are suitable for intra-articular, intra-muscular and subcutaneous injection purposes. The preparation of all these solutions under sterile conditions is readily accomplished by standard pharmaceutical techniques well known to those skilled in the art.
Additionally, it is also possible to administer the active compounds of the present invention topically when treating inflammatory conditions of the skin. This may be done by way of creams, jellies, gels, pastes, patches, ointments and the like, in accordance with standard pharmaceutical practice.
The active compounds of the present invention are useful as NOS inhibitors i.e., they possess the ability to inhibit the NOS enzyme in mammals, and therefore they are able to function as therapeutic agents in the treatment of the aforementioned disorders and diseases in an afflicted mammal.
The ability of compounds of the formulas I, II, III and IV of this invention, and their pharmaceutically acceptable salts, to inhibit NOS may be determined using procedures described in the literature. The ability of compounds of the present invention to inhibit endothelial NOS may be determined by using the procedures described by Schmidt et al. in Proc. Natl. Acad. Sci. U.S.A., 88, pp. 365-369 (1991) and by Pollock et al., in Proc. Natl. Acad. Sci. U.S.A., 88, pp. 10480-10484 (1991). The ability of compounds of the present invention to inhibit inducible NOS may be determined using the procedures described by Schmidt et al., in Proc. Natl. Acad, Sci. U.S.A., 88 pp. 365-369 (1991) and by Garvey et al. in J. Biol. Chem., 269, pp. 26669-26676 (1994). The ability of the compounds of the present invention to inhibit neuronal NOS may be determined using the procedure described by Bredt and Snyder in Proc. Natl. Acad. Sci. U.S.A., 87, 682-685 (1990).
As indicated above, inhibition of NO synthase activity may be determined by conversion of [3H]arginine to [3H]citrulline as described by Bredt and Snyder in Proc. Natl. Acad. Sci. U.S.A., 87, 682-685 (1990), but with slight modification. Specifically, 10 uL of crude enzyme lysate and 10 uL of 350 nM [3H]arginine are added to 100 uL of buffer containing 10 mM Hepes, 0.32 M sucrose, 0.75 mM NADPH, 0.1 mM EDTA, 0.63 mM CaCl2, 1 mM dithiothreitol, 30 nM calmodulin(CaM), 2 uM Flavin Adenin dinucleotie (FAD), 2 uM Flavin mononucleotide (FMN), 3 uM tetrahydrobiopterin (H4B) and trace bovine serum albumin in 96-well plate format. After incubation for 50 minutes at 30xc2x0 C., assays are terminated by application to 75 uL BioRex-70 resin (H+ form) and eluted with 90 uL of water. [3H]citrulline may be quantified by liquid scintillation spectroscopy of the total flow-through.
The title compounds of Examples 1-4 below were tested according to the foregoing procedure and each exhibited an IC50 less than 1 xcexcM for inhibition of neuronal NOS.